Population Structure and Regeneration of the Endangered Tree Fern Alsophila spinulosa in Huagaoxi National Nature Reserve, Southwestern China

Population structure and regeneration of the endangered tree fern Alsophila spinulosa in Huagaoxi National Nature Reserve were examined by life table,survival analysis and habitat (ground cover and disturbance intensity) associations. We established 44 plots (20 m × 20 m),recorded the height (H) of each tree within each plot and grouped them into ten age class:1,H < 0.01 m; 2,0.01 m ≤ H < 0.60 m; 3,0.60 m ≤ H < 1.20 m; 4,1.20 m ≤ H < 2.10 m; 5,2.10 m ≤ H < 3.00 m,and so on. Results revealed that the mean density of the A. spinulosa plots was 0.088 plants/m²,with a seedling density (class 1) of 0.049 plants/m². There were three peaks in mortality occurring in the first,seventh and tenth age classes,successively. After the seventh size class,the survival rate declined to less than 1%. Four survival function curves showed that A. spinulosa was characterized by sharp shrinkage in the early ages,stationarity in the intermediate ages and decline in the late ages. Stem density of A. spinulosa was not correlated with ground cover for any size class (p ≥ 0.18),while densities of all non-seedling individuals and the seventh size class showed a negative correlation with disturbance intensity (p < 0.05). The results suggested that the A. spinulosa population had the capacity for natural regeneration,but human interference might limit its population density.